As Jeremy said - good idea to clean up the manifold now, get a big extreme duty red trash bag and about a couple of gallons of B100 biodiesel - remove the vacuum flappers - breather plastics etc. and put in the bag and fill with diesel. leave it be for 6 or 8 hours. drain out into old oil bottles - pressure wash the nasty manifold at a car wash that allows engine cleanup - the blackness would be evil.

But the upside is that the engine will breathe really nice - like it should.

I have got manifold removal down to a timed 10 minutes now - with a makita small impact. - the joys of owning an OM606.

anyway - remove the plug with the engine blazing hot - it has the least amount of breaking chance.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)